Communication resource management device

ABSTRACT

A communication resource management device changes the transfer rate of a first control channel related to a first mobile terminal according to a communication condition. The device determines whether there is a frequency band for which it is not determined whether the frequency band is to be used in a predetermined time period based on a current transfer rate of a second control channel related to a second mobile terminal and an amount of data to be transmitted in the second control channel; and allocates, to the first mobile terminal, at least a part of the frequency band for the second control channel with respect to the second mobile terminal in a predetermined period of time. The device changes the transfer rate in the first control channel while maintaining the total frequency band for plural control channels related to plural mobile terminals at a constant value.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a U.S. continuation application, filed under 35 USC111(a) and claiming the benefit under 35 USC 120 and 365(c), of PCTapplication JP2003/000602, filed Jan. 23, 2003. The foregoingapplication is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to devices for managingcommunication resources, and more particularly, to a communicationresource management device for varying the transfer rate of a controlchannel.

2. Description of the Related Art

A user of a mobile terminal in a mobile communication system cancommunicate with a desired party by using a communication channel (orinformation channel) that is set for each call. Setting and managementof the communication channel are performed via a control channel. Inthis case, the data transfer capacity required for the control channelgenerally differs for each communication system or network. Thus, interms of effective use of communication resources, it is preferred thatallocation of communication resources for the control channel bemodified for each communication system.

In regard to this point, Japanese Patent No. 3282708 discloses atechnique for improving the efficiency in using communication resourcesby setting, for each network, an appropriate quantitative ratio on atime axis of the control channel to the information channel. A wirelessterminal in this case can establish a connection to any network having adifferent channel structure by appropriately selecting an operationalmode corresponding to each network. However, even within the same mobilecommunication system, the transfer capacity and/or traffic volumerequired for the control channel are not always the same. For example,generally, the number of control steps and the transfer quantity ofcontrol information are large at the time of connecting a call, but theyare reduced during the connection. Thus, conventional techniques such asmentioned above include problems in that it is impossible to flexiblyhandle such a communication condition.

On the other hand, in a CDMA (Code Division Multiple Access)communication system based on the specification of the 3GPP (3rdGeneration Partnership Project), a predetermined transmission band(transfer rate) is assigned for each control channel, and a fixedtransfer rate in the control channel is guaranteed in each network. Whenimproving the transfer rate in the control channel related to a certainmobile terminal, a further transmission band is allocated to the mobileterminal without modifying the allocation of transmission band withrespect to the control channels of other mobile terminals. Thereby, thedata amount that can be transferred within a given length of time isincreased in the control channel, and it becomes possible to improve thecommunication speed. A description of such a condition is given withreference to FIG. 1.

As shown in the left side of FIG. 1, among the available transmissionbands in an entire mobile communication system, a part thereof is usedfor control channels (102), another part thereof is used for acommunication channel (104), and the remaining part is emptytransmission bands (106). For example, it is assumed that, in order toguarantee a fixed transfer rate with respect to N mobile terminals, a Twtransmission band is allocated to the control channel for each of themobile terminals, and N×Tw transmission band resources are used for thecontrol channels (102) in the entire system. If two (2×Tw) transmissionbands are allocated to a certain mobile terminal in order to improve thetransfer rate of the control channel for the mobile terminal, as shownin the right side of FIG. 1, the transmission bands used for the controlchannels are (N+1)×Tw in the entire system. Since the mobile terminalcan use 2×Tw transmission bands, it becomes possible to improve thetransfer rate in the control channel.

However, when the transfer rate is improved in the aforementionedmanner, since the transmission bands allocated in a fixed manner areincreased among the available transmission bands in the entire system, aproblem occurs in that the unused bands 106 are reduced. It should benoted that the communication channels 102 include fixed transmissionbands necessary for providing various services offered in the mobilecommunication system, such as an audio channel.

When the unused bands 106 are reduced, first, the number of users thatcan be further handled in the system is decreased. In addition, sincethe empty transmission bands vary in accordance with variation in thetransmission bands occupied by the control channels, it becomesnecessary to perform transmission band management including, forexample, monitoring of the empty transmission bands. Consequently, thereis a problem in that, for example, management costs in a wireless basestation and a radio network controller (RNC) are increased. Further,since it is necessary to, for example, design a system and conductbusiness investment in consideration of the above-mentioned aspects,there is a problem in that system building is not necessarily easy.

SUMMARY OF THE INVENTION

A general object of the present invention is to provide an improved anduseful communication resource management device in which one or more ofthe above-mentioned problems are eliminated.

Another and more specific object of the present invention is to providea communication resource management device capable of effectively usingcommunication resources by varying the transfer rate of a controlchannel associated with a mobile terminal in accordance with thecommunication state.

A further object of the present invention is to provide a communicationresource management device capable of varying the transfer rate in acommunication channel associated with a mobile terminal withoutmodifying the sum of the respective transmission bands of communicationchannels allocated to plural mobile terminals.

The above-mentioned objects are achieved by the means mentioned below.According to the present invention, there is provided a communicationresource management device managing transmission bands for a pluralityof control channels related to a plurality of mobile terminals includingat least first and second mobile terminals, the communication resourcemanagement device including: first determination means for determiningwhether to change a transfer rate of a first control channel related tothe first mobile terminal; and allocation means for allocating, to thefirst mobile terminal, a transmission band for a second control channelwith respect to the second mobile terminal in a period of time based ona decision result of the first determination means, the decision resultindicating change should be made.

Other objects, features and advantages of the present invention willbecome more apparent from the following detailed description when readin conjunction with the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a breakdown of transmission bandsthat can be used in a mobile communication system;

FIG. 2 is a schematic diagram of a mobile communication system to whichthe present invention may be applied;

FIG. 3 is a block diagram of major functions of a communication resourcemanagement device according to an embodiment of the present invention;

FIG. 4 is a schematic diagram showing a breakdown of transmission bandsthat can be used in the mobile communication system;

FIG. 5 is a diagram for explaining how transmission blocks to betransferred in respective control channels are transferred on a timeaxis;

FIG. 6 is another diagram for explaining how transmission blocks to betransferred in respective control channels are transferred on a timeaxis;

FIG. 7 is a timing chart showing relationships among a transfer rate, atransmission time interval (TTI), and a transmission signal size (TFS);

FIG. 8 is a data diagram showing a general signal format;

FIG. 9 is a timing diagram showing signal transfer in downlinksaccording to a second embodiment; and

FIG. 10 is a timing diagram showing signal transfer in uplinks accordingto the second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

FIG. 2 is a schematic diagram of a mobile communication system 200 towhich the present invention may be applied. The mobile communicationsystem 200 is, for example, a CDMA communication system based on thespecification of the 3GPP. The mobile communication system 200 includesa network 202 such as the Internet, and the network 202 is provided withswitching equipment 201 for establishing a connection with anothercommunication system such as a fixed telephone network. The mobilecommunication system 200 includes radio network controllers (RNCs) 204connected to the network 202. Each radio network controller 204 controlsplural wireless base stations 206 connected thereto. Each of thewireless base stations 206 performs radio communications with a mobileterminal 208 that belongs to its own region (cell). Allocation ofcommunication resources such as the transmission bands (transfer rates)for mobile phones is managed by the radio network controller 204. InFIG. 2, Iu indicates the interface between the switching equipment 201in the network 202 and the radio network controllers 204. Iub indicatesthe interface between the radio network controllers 204 and the wirelessbase stations 206. Uu indicates the interface between the wireless basestations 206 and mobile terminals 208.

FIG. 3 is a block diagram regarding major functions of a communicationresource management device according to one embodiment of the presentinvention. For convenience of explanation, the communication resourcemanagement device 300 of this embodiment is provided in the radionetwork controller 204. However, this is not fundamental to the presentinvention, and the communication resource management device 300 may beprovided separately from the radio network controller 204. It should benoted that FIG. 3 shows major blocks related to control channels, whichare particularly important in the present invention, and those blocksrelated to processing of communication channels are omitted.

The communication resource management device 300 includes firstinterfacing means 302 for communications with the higher switchingequipment 201, and second interfacing means 304 for communications withthe lower wireless base stations 206. The first and second interfacingmeans 302 and 304 include switching means 306 for appropriatelydelivering signals in the communication resource management device 300.The communication resource management device 300 includestransmission/reception process means 308, control signal processingmeans 310, and transmission band management means 312, which are coupledto the switching means 306.

The transmission/reception process means 308 include combining means 314for receiving control signals (signals transferred in control channels)from respective mobile terminals via the first or second interfacingmeans 302 or 304, respectively, and the switching means 306 as pluralsequences of signals, and converting them into a single signal sequence.The output of the combining means 314 is connected to the switchingmeans 306. The transmission/reception process means 308 includeallocation means 316 for determining how to transfer a control signalfor each mobile terminal to a wireless base station, and dividing means318 for dividing an output signal of the allocation means 316 intoplural signal sequences for transferring.

The allocation means 316 include conversion means 320 for converting theformat of a control signal to be transferred to a mobile terminal to asignal format for the Iub from the signal format for delivering withinthe communication resource management device 300. The output of theconversion means 320 is connected to transmission time interval/sizeadjusting means 322 for adjusting the transmission time interval (TTI)of a signal or the size of data to be transferred at a time at eachtransmission cycle (TFS: Transport Format Set). The output of thetransmission time interval/size adjusting means 322 is connected to thedividing means 318. The adjustment in the transmission timeinterval/size adjusting means 322 is set under control of parametermanagement means 324 for managing a parameter that specifies, forexample, the transmission time interval. Further, the allocation means316 include special signal generation means 326 for generating a specialsignal (signal having only an Iub header) to be transmitted to a mobileterminal in the case where a transmission block (TB) to be transmittedto the mobile terminal does not exist.

The control signal processing means 310 include processing means 328 forreceiving an output signal of the combining means 314 via the switchingmeans 306 and performing, for example, analysis and determining of thecontrol signal. In addition, the processing means 328 may be used forgenerating a control signal transmitted to the mobile terminal. Thecontrol signal processing means 310 include first determination means330 for determining whether to vary the transfer rate of the controlchannel according to need (for example, in accordance with the kindand/or amount of data of a signal to be transmitted). Preferably, thecontrol signal processing means 310 further include second determinationmeans 332 for determining whether there are unused communicationresources (transmission bands) in a certain period based on the transferrate (currently) set to the control channel and the amount of data of asignal to be actually transmitted via the control channel. That is, itis also possible to consider the decision result of the seconddetermination means 332 when determining whether to vary the transferrate in the first determination means 330. The decision result in thesecond determination means 332 is also given to allocation means 316(the parameter management means 324).

The transmission band management means 312 control allocation andreleasing of transmission bands for control channels of mobile terminalsthat are used in the mobile communication system based on thetransmission bands (or the remaining transmission bands) of the controlchannels currently being used. In addition, the transmission bandmanagement means 312 serve a predetermined notice to switching equipmentand/or wireless base stations in accordance with an increase/decrease ofthe unused bands.

Referring to FIGS. 4, 5 and 6, a description is given of an operation ofthe communication resource management device 300. FIG. 4 is a schematicdiagram showing a breakdown of transmission bands in the mobilecommunication system. Similar to FIG. 1, among the availabletransmission bands in the entire system, a part thereof is used for acontrol channel 402, another part thereof is used for a communicationchannel 404, and the remaining part thereof is an unused band 406.However, in this embodiment, even if the transfer rate of the controlchannel for a certain mobile terminal is varied, unless the number (N)of mobile terminals that perform communications by using controlchannels is varied, the amount of the transmission band 402 occupied bythe control channels is maintained constant among the availabletransmission bands in the entire system. The transmission bandsmaintained constant are expressed by N×Tw, where N is the number ofmobile terminals that perform communications by using control channels,and Tw is the lowest transfer rate set and guaranteed in the mobilecommunication system in a case where each mobile terminal performscommunications by using a control channel. N and Tw are used for thesame meanings as described with reference to FIG. 1. Thus, in a casewhere each mobile terminal performs communications via its own controlchannel, as in conventional cases, each mobile terminal uses a band ofTw.

Meanwhile, in each control channel in uplinks and downlinks, data equalto or less than a predetermined data size (TFS) are transferred atpredetermined transmission time intervals. In this case, each controlchannel does not necessarily transmit data at all of the predeterminedtransmission time intervals. There may be a period during which data tobe transmitted as a control signal do not exist, that is, there is anunused communication resource that is not being used for datatransmission.

In this embodiment, such an unused communication resource is found outand allocated to a control channel related to another mobile terminal,thereby increasing the transfer rate of the communication channel.Accordingly, it becomes possible to correspond to the demand forhigh-speed control channels, and in addition, those communicationresources the use of which is not determined are used for other controlchannels. Hence, communication resources can be effectively used.Further, since all the transmission bands 402 for control channels aremaintained constant among the available transfer channels in the entiresystem, it is possible to avoid reducing the transmission bands 404 forcommunication channels and the remaining transmission bands 406.Accordingly, it is possible to eliminate various problems caused byreducing the remaining transmission bands 406.

FIG. 5 shows how transmission blocks 502 (1-1, 1-2, . . . , 1-6, 2-1, .. . , 4-4), which should be transmitted via corresponding four controlchannels CH1 through CH4 are transferred with respect to a time axis504. FIG. 5 shows signals in cases (A) and (B) where the radio networkcontroller (RNC) 204 transmits, to the wireless base station 206 (andthe mobile terminal 208), the contents of a signal (transmission blocks)generated by the RNC 204 or received from the higher level switchingequipment 201. (A) shows the case where transmission is performed toeach mobile terminal within the transfer rate guaranteed in the system.(B) shows the case where the transfer rate of a control channel 1 isincreased, but the transfer rates of the other control channels aremaintained as is.

First, transmission blocks to be transmitted in each control channel areaccumulated (buffered) in the radio network controller 204. As for thecontrol channel 1 (CH1), transmission blocks 1-1 through 1-4 areconsecutively received or created, and then transmission blocks 1-5through 1-6 are received and accumulated in preparation fortransmission. As for the control channel 2 (CH2), transmission blocks2-1, 2-2 and 2-3 are intermittently received, and each of them areaccumulated in preparation for transmission. As for the control channel3 (CH3) and the control channel 4 (CH4), similarly, transmission blocks3-1 through 3-4 and 4-1 through 4-4 are received and accumulated,respectively. It should be noted that, for simplicity, the timings forbuffering transmission blocks are illustrated as if they are the same asthe timings for transmitting the transmission blocks. However, actually,each transmission block is transmitted after a predetermined time periodelapses since being buffered.

First, in the case of (A), it is possible to transfer a signal in eachcontrol channel with the use of the minimum band Tw that is guaranteedin the system. As shown in FIG. 5, if there are data, transmissionblocks of each control channel may be transmitted at intervals of 40 msat latest. In this regard, a technique according to an embodiment of thepresent invention and the conventional technique (FIG. 1) offer similarresults.

Next, a description is given of the case where the transfer rate of thecontrol channel (CH1) is increased. Determination of whether to increasethe transfer rate of the control channel 1 may be based on, for example,whether the data amount (traffic volume) to be transmitted via thecontrol channel 1 exceeds a predetermined value. The transfer rate ofthe control channel 1 may be increased in the case where a predeterminedcontrol step is started or the case where a predetermined message istransmitted, such as when a call is established or released. In anycase, it is preferable to increase the transfer rate in the case wherethe number of control steps performed via the control channel withrespect to a mobile station is increased or the amount of controlsignals transferred is increased. The determination is made by the firstdetermination means 330 of the control signal processing means 310, andis communicated to the parameter management means 324.

Preferably, it is further determined in the second determination means332 whether there is a communication resource that will be unused in thefuture in the control channels other than the control channel 1. It ispossible to find a communication resource that will be unused based onthe transfer rate currently set to each control channel and the amountof data of transmission blocks accumulated in each control channel foractual transmission. For example, assuming fixed terms T1, T2, T3 andT4, each having a time length of 40 ms, transmission of the transmissionblock 2-1, which is transferred via the control channel 2, is completedduring the term T1 (the data size thereof is that much). Hence,communication resources reserved for the control channels 2, such asblocks 506 indicated by dotted lines, will be unused during the terms T2and T3. Similarly, as for the control channels 3 and 4, it turns outthat communication resources will be unused during the terms T2 and T3.It is not essential that the fixed term assumed for finding unusedcommunication resources matches the transmission interval in the case ofthe guaranteed minimum transfer rate, such as 40 ms, and another fixedterm may be assumed as well.

By allocating, to the control channel 1, the communication resources forthe control channel 2 and the control channel 3 found to be unused inthe aforementioned manner, signal transfer as shown in (B) is performed.That is, in the Term T1, transmission blocks are transmitted atintervals of 40 ms in the control channel 1. In the terms T2 and T3,transmission blocks are transmitted at intervals of 10 ms in the controlchannel 1. Transmission of up through the transmission block 1-6 iscompleted within the term T3. Thereby, compared to the case of (A), itis possible to complete transmission in the control channel 1 within ahalf period.

Preferably, in the communication resource management device 300, apositive decision result (indicating necessity of modification and thatthere will be unused resources in the future) of the first determinationmeans 330 and the second determination means 332 is communicated to theallocation means 316, and what to transmit at what timing is set. Forexample, as for the control channel 1, transmission blocks aretransmitted at intervals of 40 ms in the term T1. In the term T2,transmission blocks are not transmitted at intervals of 40 ms, but thetransmission blocks 1-2, 1-3 and 1-4 are transferred at intervals of 10ms with the use of communication resources for the control channels 2and 3. Also in the term T3, the transmission blocks 1-5 and 1-6 aretransferred at intervals of 10 ms. In order to realize such transfer,various parameters are adjusted. The parameter management means 324 sendinstructions to the transmission time interval/size adjusting means 322such that the minimum transfer rate guaranteed in the system is realizedin the term T1 and a higher transfer rate is realized in the terms T2and T3. In accordance with the instructions, the transmission timeinterval/size adjusting means 322 adjust the transmission time intervalsor data size.

The set items such as transmission time interval TTI and thetransmission data size TFS, which are varied by the control signalprocessing means 310 and the allocation means 316, are communicated to acorresponding wireless base station and a wireless base station and amobile terminal that are related to a control channel to be varied.Then, it becomes possible for the radio network controller to performcommunications via a control channel having a newly set transfer rate.It should be noted that, in this case, the transmission band managementmeans 312 need not specifically manage allocation of communicationresources in each control channel between a mobile terminal and awireless base station. As mentioned above, the transmission bandmanagement means 312 control allocation and releasing of communicationresources for control channels with respect to mobile terminals that areused in the mobile communication system. Hence, the transmission bandmanagement means 312 have only to recognize how much unused bands areleft in the entire system. Different from conventional techniques, inthis embodiment, if the number (N) of mobile terminals performingcommunications with the use of control channels is not changed, thetransmission bands 402 (=N×Tw) for control channels used in the entiresystem are not changed. Thus, the unused bands 406 are not changed aswell. The control signal processing means 310 and the allocation means316 can determine how to allocate transmission bands in the transmissionbands 402 for control channels, without using the transmission bandmanagement means 312. Further, the radio network controller mayunilaterally transmit varied set items to a mobile terminal beforestarting variation of a wireless base station, and may vary the transferrate in a control channel without transmitting a signal to and/orreceiving a signal from the mobile terminal.

In the example shown in FIG. 5, the description has been given of therate in which transmission is made at intervals of 40 ms and the rate inwhich transmission is made at intervals of 10 ms. However, the number ofkinds of transfer rate may be increased. For example, options forperforming transmission at intervals of 10 ms, 20 ms, 30 ms and 40 msmay be provided and suitably selected.

The transmission time interval, such as 10 ms and 40, ms may beassociated with a delay time until a signal is buffered and transmitted,i.e., quality of service (QoS). For example, a signal receivedimmediately after the transmission cycle of 10 ms is buffered forapproximately 10 ms and transmitted at the next transmission timing.Thus, the delay time of a signal is different between the case where thetransmission time interval is 10 ms and the case where the transmissiontime interval is 40 ms, and the QoS is also different between thesecases. Hence, it is advantageous to divide the QoS realized in thesystem into two or more classes in advance (for example, thetransmission time interval TTI=40 ms may represent a first class QoS1,and the transmission time interval TTI=10 ms may represent a secondclass QoS2), to select an appropriate class according to need, and toadjust the transfer rate in a control channel, thereby managingallocation of frequency bands. For example, the QoS may also be used inan operation of a management timer in an ARQ (Automatic Repeat Request),and may be used for signal processing other than transmission bandallocation.

Meanwhile, even with the conventional technique as described withreference to the right side of FIG. 1, it is possible to increase therate in the control channel 1 as shown in (B) of FIG. 5. However, insuch a case, the unused bands will be reduced in return for increasingthe rate in the control channel. It should be noted that, according toan embodiment of the present invention, under the condition that unusedcommunication resources in control channels are found, it becomespossible to increase the rate in any of the control channels withoutreducing the unused bands.

On the other hand, when the decision result in the second determinationmeans 332 of the communication resource management device 300 isnegative, it implies that there are no such communication resources thatare not going to be used during a predetermine term such as T2 and T3 inthe communication resources for the control channels other than thecontrol channel 1. It is desirable that all control channels guaranteethat communications may be performed at a predetermined communicationrate or a higher communication rate. It is undesirable for thecommunication rate of another control channel having data to betransmitted to be reduced for increasing the communication rate of acertain control channel. Accordingly, as shown in FIG. 6, in the casewhere each control channel includes a large amount of data to betransmitted and is congested, even if the decision result in the firstdetermination means 330 indicates necessity of variation, the seconddetermination means 332 send notification that there will be noresources available. Thus, the allocation means 316 do not approvevariation of the transfer rate, and each control channel transmits itsown transmission blocks at the minimum rate guaranteed in the system. Inthe example shown in FIG. 6, each of the control channels 1 through 4transmits its own transmission blocks at intervals of 40 ms.

In the above description, the transmission transfer interval (TTI) isadjusted so as to vary the transfer rate of a control channel. However,the data size (TFS) of data to be transmitted at a time as well as thetransmission time interval may be varied so as to vary the transferrate.

FIG. 7 shows conditions where transfer rates are varied by varying thetransmission time intervals or the data size. Each timing chart shows acondition where transmission blocks TB1 through TB4, each having apredetermined data size, are transferred from a transmitting node to areceiving node. In the timing chart indicated by (A), one transmissionblock is transferred at transmission time intervals of a first term D1.In the timing chart indicated by (B), one transmission block istransferred at transmission time intervals of a second term D2, which isa half of the first term D1. In this manner, a transfer rate twice thetransfer rate in the case indicated by (A) is achieved. In the timingchart indicated by (C), two transmission blocks are transferred attransmission time intervals of the first term D1. Also in this manner,it is possible to achieve a transfer rate twice the transfer rate in thecase indicated by (A). Further, though not shown in the figure, it isalso possible to further increase or decrease the transfer rate byadjusting both transmission time interval and data size.

As mentioned above, according to this embodiment, it is possible toeffectively use communication resources by varying the transfer rate ina control channel related to a mobile terminal in accordance with acommunication condition. Additionally, according to this embodiment, itis possible to vary the transfer rate in a control channel related toeach mobile terminal without varying the sum of transmission bands forcontrol channels.

In the above description, the transfer rate of only one control channelis increased. However, the transfer rates of a greater number of controlchannels may be increased. Further, a particular description has notbeen given of variation in the wireless zone between a wireless basestation and a mobile terminal due to variation in a transfer rate (e.g.,twice). However, in the case where, for example, wireless communicationsare being performed with the use of a spread code A (spread rate x), itis possible to vary a transfer rate in the wireless zone by newlyassigning a spread code B (spread rate x).

Second Embodiment

Data transfer from a transmitting node to a receiving node is performedsuch that a signal of a predetermined data size, such as 1 block or 2blocks, is transferred at predetermined transmission time intervals(TTI) such as 10 ms or 40 ms. Generally, the format of a signaltransmitted from and received by a radio network controller (RNC) is asshown in FIG. 8 and includes a header 802 and a subsequent payload 804.The payload 804 includes transmission blocks 1, 2, 3, . . . to betransferred. The header 802 includes a transport format indicator (TFI),which indicates the number or amount of the transmission blocks (TB)following the header. Although an actual TFI is a value related to thedata amount of transmission blocks, the actual TFI is not always anumeric value directly representing the number of transmission blocks.However, for convenience of explanation, it is assumed that a TFIdirectly represents the number of transmission blocks. For example, whenTFI=3, then 3 transmission blocks (TB1, TB2, TB3) are included in apayload as shown in FIG. 8. In addition, the data amount of atransmission block is also determined in advance, which may be, forexample, 40 bytes/packet.

When transferring transmission blocks, of course the transmission blocksare transferred at predetermined transmission time intervals by using asignal format as mentioned above. However, conventionally, even whenthere is no transmission block to be transmitted, certain signals havebeen transmitted at transmission time intervals. For example, whenestablishing a call, relatively many signals are transferred. However,in a stabilized period after a connection is established, the number oftransmission blocks to be transferred by using a control channel issignificantly decreased. In this case, the signal may not be transferredat transmission cycles defined by a TTI. However, in such a case, thereis concern that the transmitting node and the receiving node may not besynchronized. Thus, even if there is no transmission block to betransmitted, a special signal (or NoDATA signal), such as a signalhaving only the header 802, is transferred at transmission cycles. Inthe case where a wireless base station has not received any signalduring a predetermined time frame, the wireless base station canmaintain synchronization between nodes by transmitting a time adjustment(TA) signal. The TFI included in NoDATA indicates that the number oftransmission blocks is 0 (TFI=0).

It is contemplated to apply such a technique to the above-mentionedfirst embodiment. For example, it is assumed that a first mode wheretransmission is performed at the minimum transfer rate of 40 ms and asecond mode where transmission is performed at the maximum transfer rateof 10 ms are prepared. In this case, in the first mode, transmissionblocks TB or special signals are transmitted at intervals of 40 ms. Inthe second mode, transmission blocks TB or special signals aretransmitted at intervals of 10 ms.

However, the intended purpose of the second mode is high speed transferof transmission blocks. Thus, when there is no transmission block to betransmitted, it is impractical to perform high speed transfer byincreasing traffic by using frequency resources for another controlchannel.

Hence, in this embodiment, in addition to a transmission time intervalfor transferring transmission blocks TB, another transmission timeinterval is prepared for transferring special signals (NoDATA signals),and the latter is set longer than the former. In the above-mentionedexample, transmission blocks are transmitted at intervals of 10 ms inthe second mode. However, when there is no transmission block, specialsignals (NoDATA signals) can be transmitted at intervals of 40 ms.Additionally, in the first mode, transmission blocks and special signalsare transmitted at intervals of 40 ms.

FIG. 9 is a timing chart showing signal transfer in a downlink accordingto the second embodiment. FIG. 9 shows a condition (A) where a wirelessnetwork controller (RNC) (more properly, the communication resourcemanagement device 300) receives control signals (transmission blocks)1-1 and 1-2 from the higher switching equipment 201, and a condition (B)where the radio network controller transmits the control signals 1-1 and1-2 to a wireless base station under the radio network controller. Forconvenience of explanation, the communication resource management device300 is set to operate in the second mode, which is the high speed mode.Thus, as indicated by (B), the transmission blocks 1-1 and 1-2 to betransmitted are transmitted to the wireless base station at transmissiontime intervals of 10 ms. Since there are no more transmission blocks,after the transmission blocks 1-1 and 1-2 are transmitted, specialsignals S are transmitted at intervals of 40 ms. The special signals Sare created by special signal generation means 336 under management ofthe parameter management means 324 in the allocation means 316, and aresupplied to the transmission time interval/size adjusting means 322. Itshould be noted that the dotted lines shown in (B) represent specialsignals created and transmitted when TTI for the special signals S arenot prepared.

In the example shown in the figure, the special signals S aretransmitted at intervals of 40 ms from a predetermined time point thatis set for the special signals S. However, this is not necessary for thepresent invention, and transmission may be made from an arbitrary timepoint after the transmission block 1-2 is transmitted. For example,transmission may be made at intervals of 40 ms after the lasttransmission block (1-2) is transmitted.

FIG. 10 is a timing diagram showing signal transfer in uplinks accordingto the second embodiment. FIG. 10 shows the case (B) where thecommunication resource management device 300 receives control signals(transmission blocks) 1-1 and 1-2 from the mobile terminal 208 and thewireless base station and the case (A) where these are transmitted tothe switching equipment 201. Also in this case, the communicationresource management device 300 is set to operate in the above-mentionedsecond mode, which is the high-speed mode. Accordingly, as shown in (A),the received transmission blocks 1-1 and 1-2 are transmitted to higherswitching equipment at intervals of 10 ms. Although there are no moretransmission blocks, the communication resource management device 300receives special signals S at intervals of 40 ms even after receivingthe transmission block 1-2. Further, the dotted lines shown in (B)represent special signals to be received when TTI for the specialsignals S are not prepared. In the example shown in the figure, thespecial signals S are transmitted at intervals of 40 ms from the timepoint set for the special signals S. However, as described withreference to FIG. 9, transmission may be made from another time point.

According to this embodiment, in addition to the effect of the firstembodiment, which increases the speed of the control channel, there isno need to frequently transfer special signals such as NoDATA. Hence, itis possible to use communication resources related to a decrease intraffic for other communications. Thus, it is possible to moreeffectively use communication resources.

The present invention is not limited to the specifically disclosedembodiments, and variations and modifications may be made withoutdeparting from the scope of the present invention.

The present application is based on Japanese priority application No.2002-246655 filed on Aug. 15, 2002, the entire contents of which arehereby incorporated herein by reference.

1. A communication resource management device managing transmissionbands for a plurality of control channels related to a plurality ofmobile terminals including at least first and second mobile terminals,said communication resource management device comprising: firstdetermination means for determining whether to change a transfer rate ofa first control channel related to the first mobile terminal; andallocation means for allocating, to said first mobile terminal, atransmission band for a second control channel with respect to saidsecond mobile terminal in a period of time based on a decision result ofthe first determination means, the decision result indicating changeshould be made.
 2. The communication resource management device asclaimed in claim 1, further comprising: second determination means fordetermining whether there is unused transfer band for the second controlchannel in a predetermined time period based on a current transfer rateof the second control channel related to the second mobile terminal andan amount of data of signals to be transmitted in the second controlchannel.
 3. The communication resource management device as claimed inclaim 1, wherein the period of time is a positive integer multiple of atransmission time interval (TTI) of signals.
 4. The communicationresource management device as claimed in claim 1, wherein the firstdetermination means is configured to make a decision that the transferrate should be changed when a call is established or released.
 5. Thecommunication resource management device as claimed in claim 1, whereinthe first determination means is configured to make a decision based ona change in traffic volume in the first control channel.
 6. Thecommunication resource management device as claimed in claim 1, whereinthe first and second control channels are controlled to have at leastpredetermined first and second qualities of services (QoS),respectively.
 7. The communication resource management device as claimedin claim 6, wherein a transmission time interval (TTI) of signalstransferred with the first quality of service and a transmission timeinterval (TTI) of signals transferred with the second quality of serviceare set to be different from each other.
 8. The communication resourcemanagement device as claimed in claim 7, wherein a data signaltransferred to a mobile terminal by using the first control channel istransferred at narrow transmission time intervals, and in a period oftime where there is no data signal transferred to the mobile terminal, asignal (NoDATA) for maintaining synchronization with the mobile terminalis transferred at wide transmission time intervals.
 9. The communicationresource management device as claimed in claim 6, wherein a signal size(TFS) per unit of time of a signal transferred with the predeterminedfirst quality of service and a signal size (TFS) per unit of time of asignal transferred with the predetermined second quality of service areset to be different from each other.
 10. The communication resourcemanagement device as claimed in claim 6, wherein the predetermined firstquality of service is defined such that a signal is transmitted at aminimum data transfer rate guaranteed in a communication system, and thepredetermined second quality of service is defined such that a signal istransferred at a rate equal to or higher than the minimum data transferrate.
 11. A wireless network control apparatus comprising thecommunication resource management device as claimed in claim 1 andcontrolling a plurality of wireless base stations that communicate witha plurality of mobile terminals.